Device news032412


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  • microscope image of the tungsten photonic crystal structure reveals the precise uniform spacing of cavities formed in the material, which are tuned to specific wavelengths of light. Image courtesy of Y.X. Yeng et al.A team of MIT researchers has developed a way of making a high-temperature version of a kind of materials called photonic crystals, using metals such as tungsten or tantalum. The new materials — which can operate at temperatures up to 1200 degrees Celsius — could find a wide variety of applications powering portable electronic devices, spacecraft to probe deep space, and new infrared light emitters that could be used as chemical detectors and sensors.Compared to earlier attempts to make high-temperature photonic crystals, the new approach is “higher performance, simpler, robust and amenable to inexpensive large-scale production.
  • at Rice University are using carbon nanotubes as the critical component of a robust terahertz polarizer that could accelerate the development of new security and communication devices, sensors and non-invasive medical imaging systems as well as fundamental studies of low-dimensional condensed matter systems. It is the most effective polarizer ever reported; it selectively allows 100 percent of a terahertz wave to pass or blocks 99.9 percent of it, depending on its polarization.The broadband polarizer handles waves from 0.5 to 2.2 terahertz, far surpassing the range of commercial polarizers that consist of fragile grids wrapped in gold or tungsten wires. Kono said technologies that make use of the optical and electrical regions of the electromagnetic spectrum are mature and common, as in lasers and telescopes on one end and computers and microwaves on the other. But until recent years, the terahertz region in between was largely unexplored. "Over the past decade or two, people have been making impressive progress," he said, particularly in the development of such sources of radiation as the terahertz quantum cascade laser.
  • detector and terahertz generator in graphene..Sketch of the FDTD simulation geometry. Metal strips are indicated in yellow, the substrate in green and grey. Fair and Fwg indicate rectangular areas for calculating the passing field flux above and in the stripline circuit, respectively. (b) Field flux Fwg (solid black line) and field flux Fair (dashed black line) as a function of frequency f in the FDTD simulation. The centre frequency is f=0.3 THz with a frequency width Δf=0.2 THz. Field fluxes for a simulation geometry without metal strips and trench are strongly reduced (Fwg red line, Fair dashed red line). (c) Finite-element-method simulation of the effective index of diffraction neff as a function of frequency f with (black circles) and without (full red circles) a trench. Solid lines are guides to the eye.Graphene, a two-dimensional layer of carbon atoms, is a promising building block for a wide range of optoelectronic devices owing to its extraordinary electrical and optical properties, including the ability to absorb ~2% of incident light over a broad wavelength range. While the RC-limited bandwidth of graphene-based photodetectors can be estimated to be as large as 640 GHz, conventional electronic measurement techniques lack for analysing photocurrents at such frequencies. Here we report on time-resolved picosecond photocurrents in freely suspended graphene contacted by metal electrodes. At the graphene–metal interface, we demonstrate that built-in electric fields give rise to a photocurrent with a full-width-half-maximum of ~4 ps and that a photothermoelectric effect generates a current with a decay time of ~130 ps. Furthermore, we show that, in optically pumped graphene, electromagnetic radiation up to 1 THz is generated. Our results may prove essential to build graphene-based ultrafast photodetectors, photovoltaic cells and terahertz sources.
  • at Oregon State University have discovered a way to make a low-cost material that might accomplish negative refraction of light and other radiation – a goal first theorized in 1861 by a giant of science, Scottish physicist James Maxwell, that has still eluded wide practical use.“Other materials can do this but they are based on costly, complex crystalline materials. A low-cost way that yields the same result will have extraordinary possibilities, experts say – ranging from a “super lens” to energy harvesting, machine vision or “stealth” coatings for seeming invisibility.The new approach uses ultra-thin, ultra-smooth, all-amorphous laminates, essentially a layered glass that has no crystal structure. It is, the researchers say, a “very high-tech sandwich.” The goal is to make radiation bend opposite to the way it does when passing through any naturally occurring material.”Metamaterial holograms their latest series of experiments, the Duke team demonstrated that a metamaterial construct they developed could create holograms—like the images seen on credit or bank cards—in the infrared range of light, something that had not been done before.The Duke engineers point out that while this advance was achieved in a specific wavelength of light, the principles used to design and create the metamaterial in their experiments should apply in controlling light in most frequencies."In the past, our ability to create optical devices has been limited by the properties of natural materials," said StéphaneLarouche, research scientist in electrical and computer engineering at Duke's Pratt School of Engineering. "Now, with the advent of metamaterials, we can almost do whatever we want to do with light."In addition to holograms, the approach we developed easily extends to a broad range of optical devices," Larouche said. "If realized, full three-dimensional capabilities open the door to new devices combining a wide range of properties. Our experiments provide a glimpse of the opportunities available for advanced optical devices based on metamaterials that can support quite complex material properties.”Wireless Power Transfer of Applied Physics - Magnetic superlens-enchanced inductive coupling for wireless power transferResearchers from Duke University in Durham, N.C., and the Mitsubishi Electric Research Laboratories in Cambridge, Mass., have proposed a way to enhance the efficiency of wireless power transfer systems by incorporating a lens made from a new class of artificial materials.A superlens has a property call negative permeability. This means it can refocus a magnetic field from a source on one side of the lens to a receiving device on the other side. By running numerical calculations, the team determined that the addition of a superlens should increase system performance, even when a fraction of the energy was lost by passing through the lens.When the researchers first began studying how a superlens might affect wireless energy transfer, they focused on lenses made from metamaterials that exhibited uniform properties in all directions. In their new study, accepted for publication in the American Institute of Physics’ Journal of Applied Physics, the team also considered materials with magnetic anisotropy, meaning the magnetic properties are directionally dependent. Their results suggest that strong magnetic anisotropy of the superlens can offer further improvements to the system, such as reduction of the lens thickness and width.
  • 50 picometer resolution super microscope without lens. a recent paper published in Nature on March 6, 2012 under the daunting title of “Ptychographic electron microscopy using high-angle dark-field scattering for sub-nanometre resolution imaging," University of Sheffield scientists M.J. Humphry, B. Kraus, A.C. Hurst, A.M. Maiden and principal investigator John M. Rodenburg outlined their achievements in overcoming some of the limitations that have held back the potential of the electron microscopeResearchers at the University of Sheffield have created what sounds impossible - even nonsensical: an experimental electron microscope without lenses that not only works, but is orders of magnitude more powerful than current models. By means of a new form of mathematical analysis, scientists can take the meaningless patterns of dots and circles created by the lens-less microscope and create images that are of high resolution and contrast and, potentially, up to 100 times greater magnification.Diffractive imaging, in which image-forming optics are replaced by an inverse computation using scattered intensity data, could, in principle, realize wavelength-scale resolution in a transmission electron microscope. However, to date all implementations of this approach have suffered from various experimental restrictions. Here we demonstrate a form of diffractive imaging that unshackles the image formation process from the constraints of electron optics, improving resolution over that of the lens used by a factor of five and showing for the first time that it is possible to recover the complex exit wave (in modulus and phase) at atomic resolution, over an unlimited field of view, using low-energy (30 keV) electrons. Our method, called electron ptychography, has no fundamental experimental boundaries: further development of this proof-of-principle could revolutionize sub-atomic scale transmission imaging.a) Experiments were carried out on an FEI Quanta 600 SEM fitted with a thermally assisted Schottky field emission gun and operating at 30 keV. The probe wavefront was formed using the microscope condenser and objective lenses and was scanned across the specimen using the microscope scanning coils. The specimen was mounted on a compact rig attached to the objective lens pole piece assembly. The door of the microscope was replaced in order to accommodate a flange for a GatanOrius SC200 CDD camera that was cantilevered into a position below the specimen plane.b) The full field-of-view is shown in the inset image (scale bar, 15 nm); the main image is a blow up of the region indicated by the yellow box, showing 0.236 nm atomic plane fringes (scale bar, 5 nm). The modulus and phase of the reconstructions are combined in these images, with phase represented by colour and modulus by brightness, as indicated on the colour wheel scale.
  •“The integration of electronics with materials opens up a world of possibilities, the surface of which is just being scratched. Professor Arokia Nathan has joined the University to take up a new Chair in Engineering, where he will be exploring the application of research that allows us to glimpse a world rivalling our wildest dreams of the future.”The potential applications for nanophotonics and nanoelectronics are truly startling, suggesting the brink of a revolution in human–machine interfaces that could turn science fiction into a reality. From interactive paper to clothing that generates energy and light-weight material with X-ray capabilities, weaving electronics into the building blocks of everyday materials will undoubtedly impact how we live in the future.Nanowires will be a key area of investigation for Nathan in the coming years. These structures have an extraordinary length-to-width ratio, only a few nanometres in diameter, and a much greater capacity in terms of speed. “Uniformly dispersed over large areas, the wires could result in millions of transistors on a single sheet of A4 for example,” says Nathan.“While it hasn’t been done yet, we will be working on this in an attempt to match the speeds of a Pentium-like chip, scaled to A4. Pentium chips cost 10 dollars per centimetre squared, while a nano thin film transistor could cost as little as 10 cents per centimetre squared, a much cheaper alternative.”Industries such as biomedicine could also benefit hugely from this interlacing of nano-electronics into materials. “You could foresee a time when you can take the X-ray to the patient rather than vice-versa,” says Nathan. “Patients might lie on a surface woven with electronics, so that data can be broadcast straight from the material. You couldn’t do this with Pentium-like chips because of yield and cost issues.”
  • from Stanford University and the U.S. Department of Energy’s SLAC National Accelerator Laboratory have created the first-ever system of “designer electrons” – exotic variants of ordinary electrons with tunable properties that may ultimately lead to new types of materials and devices.“The behavior of electrons in materials is at the heart of essentially all of today’s technologies,” said HariManoharan, associate professor of physics at Stanford and a member of SLAC’s Stanford Institute for Materials and Energy Sciences, who led the research. “We’re now able to tune the fundamental properties of electrons so they behave in ways rarely seen in ordinary materials.”Precisely positioned carbon monoxide molecules (black) guide electrons (yellow-orange) into a nearly perfect honeycomb pattern called molecular graphene. Electrons in this structure have graphene-like properties; for example, unlike ordinary electrons, they have no mass and travel as if they are moving at the speed of light in a vacuum.This graphic shows the effect that a specific hexagonal pattern of carbon monoxide molecules (black/red) has on free-flowing electrons (orange/yellow) atop a copper surface. Ordinarily, the electrons behave as simple plane waves (background). But the electrons are repelled by the carbon monoxide molecules, placed here in a hexagonal pattern.This forces the electrons into a honeycomb shape mimicking the electronic structure of graphene, a pure form of carbon that has been widely heralded for its potential in future electronics. The molecules are precisely positioned with the tip of a scanning tunneling microscope (blue).Image courtesy HariManoharan/Stanford University“One of the wildest things we did was to make the electrons think they are in a huge magnetic field when, in fact, no real field had been applied,”Manoharan said. Guided by the theory developed by co-author Francisco Guinea of Spain, the Stanford team calculated the positions where carbon atoms in graphene should be to make its electrons believe they were being exposed to magnetic fields ranging from zero to 60 Tesla, more than 30 percent higher than the strongest continuous magnetic field ever achieved on Earth. The researchers then moved carbon monoxide molecules to steer the electrons into precisely those positions, and the electrons responded by behaving exactly as predicted – as if they had been exposed to a real field.
  • More designer electrons above is the final output of a nanoscale assembly in movie form at Graphene PNP Junction Device. Stretching or shrinking the bond lengths in molecular graphene corresponds to changing the concentrations of Dirac electrons present. This image shows three regions of alternating lattice spacing sandwiched together. The two regions on the ends contain Dirac "hole" particles (p-type regions), while the region in the center contains Dirac "electron" particles (n-type region). A p-n-p structure like this is of interest in graphene transistor applications.
  • Wired - By 2017, HP hopes to build a computer chip that includes 256 microprocessors tied together with beams of light. Codenamed Corona, this laser-powered contraption would handle ten trillion floating points operations a second. In other words, if you put just five of them together, you’d approach the speed of today’s supercomputers. The chip’s 256 cores would communicate with each other at an astonishing 20 terabytes per second, and they’d talk to memory at 10 terabytes a second. That means it would run memory-intensive applications about two to six times faster than an equivalent chip made with good old fashioned electric wires.Codenamed Corona, this laser-powered contraption would handle 10 trillion floating points operations a second. In other words, if you put just five of them together, you’d approach the speed of today’s supercomputers. The chip’s 256 cores would communicate with each other at an astonishing 20 terabytes per second, and they’d talk to memory at 10 terabytes a second. That means it would run memory-intensive applications about two to six times faster than an equivalent chip made with good, old-fashioned electric wires.More importantly, Corona would use a lot less power, helping the world’s supercomputers break the vaunted exascale barrier — i.e., deliver a machine that can handle one quintillion (10 to the 18th) floating point operations a second. That’s 100 times faster than today’s fastest supercomputer. “Electronics … cannot scale to the scale that we need for these large systems,” says HP Labs researcher Marco Fiorentino.3Corona is just one of several efforts to build superfast chips that can bust through the exascale barrier, including Intel’s Runnemede, MIT’s Angstrom, NVIDIA’s Echelon,andSandia’s X-calibur projects. All seek to use integrated photonics in some way, but the technology is the heart of the matter for HP’s 256-core Corona. – one atomic plane of carbon – is a remarkable material with endless unique properties, from electronic to chemical and from optical to mechanical.One of many potential applications of graphene is its use as the basic material for computer chips instead of silicon. This potential has alerted the attention of major chip manufactures, including IBM, Samsung, Texas Instruments and Intel. Individual transistors with very high frequencies (up to 300 GHz) have already been demonstrated by several groups worldwide.Unfortunately, those transistors cannot be packed densely in a computer chip because they leak too much current, even in the most insulating state of graphene. This electric current would cause chips to melt within a fraction of a second.“An obstacle to the use of graphene as an alternative to silicon electronics has been the absence of an energy gap between its conduction and valence bands, which makes it difficult to achieve low power dissipation in the OFF state. We report a bipolar field-effect transistor that exploits the low density of states in graphene and its one atomic layer thickness. Our prototype devices are grapheneheterostructures with atomically thin boron nitride or molybdenum disulfide acting as a vertical transport barrier. They exhibit room temperature switching ratios of ≈50 and ≈10,000 respectively. Such devices have potential for high-frequency operation and large-scale integration.”The University of Manchester scientists now suggest using graphene not laterally (in plane) – as all the previous studies did – but in the vertical direction. They used graphene as an electrode from which electrons tunnelled through a dielectric into another metal. This is called a tunnelling diode.Graphene alone would not be enough to make the breakthrough. Fortunately, there are many other materials, which are only one atom or one molecule thick, and they were used for help.The Manchester team made the transistors by combining graphene together with atomic planes of boron nitride and molybdenum disulfide. The transistors were assembled layer by layer in a desired sequence, like a layer cake but on an atomic scale.Such layer-cake superstructures do not exist in nature. It is an entirely new concept introduced in the report by the Manchester researchers. The atomic-scale assembly offers many new degrees of functionality, without some of which the tunnelling transistor would be impossible.“The demonstrated transistor is important but the concept of atomic layer assembly is probably even more important,” explains Professor Geim.Professor Novoselov added: “Tunnelling transistor is just one example of the inexhaustible collection of layered structures and novel devices which can now be created by such assembly.
  • Straintronics: Engineers create piezoelectric graphene illustration shows lithium atoms (red) adhered to a graphene lattice that will produce electricity when bent, squeezed or twisted. Conversely, the graphene will deform when an electric field is applied, opening new possibilities in nanotechnology. Illustration: Mitchell Ong, Stanford School of EngineeringIn what became known as the ‘Scotch tape technique,” researchers first extracted graphene with a piece of adhesive in 2004. Graphene is a single layer of carbon atoms arranged in a honeycomb, hexagonal pattern. It looks like chicken wire.Graphene is a wonder material. It is a one-hundred-times-better conductor of electricity than silicon. It is stronger than diamond. And, at just one atom thick, it is so thin as to be essentially a two-dimensional material. Such promising physics have made graphene the most studied substance of the last decade, particularly in nanotechnology. In 2010, the researchers who first isolated it shared the Nobel Prize.Yet, while graphene is many things, it is not piezoelectric. Piezoelectricity is the property of some materials to produce electric charge when bent, squeezed or twisted. Perhaps more importantly, piezoelectricity is reversible. When an electric field is applied, piezoelectric materials change shape, yielding a remarkable level of engineering control.“The physical deformations we can create are directly proportional to the electrical field applied. This represents a fundamentally new way to control electronics at the nanoscale,” said Evan Reed, head of the Materials Computation and Theory Group at Stanford and senior author of the study.This phenomenon brings new dimension to the concept of ‘straintronics,’ he said, because of the way the electrical field strains—or deforms—the lattice of carbon, causing it to change shape in predictable ways.“Piezoelectric graphene could provide an unparalleled degree of electrical, optical or mechanical control for applications ranging from touchscreens to nanoscale transistors,” said Mitchell Ong, a post-doctoral scholar in Reed’s lab and first author of the paper.While the results in creating piezoelectric graphene are encouraging, the researchers believe that their technique might further be used to engineer piezoelectricity in nanotubes and other nanomaterials with applications ranging from electronics, photonics, and energy harvesting to chemical sensing and high-frequency acoustics.
  • Printing three dimensional objects with incredibly fine details is now possible using “two-photon lithography”. With this technology, tiny structures on a nanometer scale can be fabricated. Researchers at the Vienna University of Technology (TU Vienna) have now made a major breakthrough in speeding up this printing technique: The high-precision-3D-printer at TU Vienna is orders of magnitude faster than similar devices (see video). This opens up completely new areas of application, such as in medicine.Ultra-high-resolution 3D Printer is breaking speed-records at the Vienna University of Technology. The 3D printed lines are a few hundred nanometers wide. It might become possible with metamaterials to reduce the lines to tens of nanometers. 100 layers, consisting of approximately 200 single lines each, are produced in four minutes. Because of the dramatically increased speed, much larger objects can now be created in a given period of time. This makes two-photon-lithography an interesting technique for industry. At the TU Vienna, scientists are now developing bio-compatible resins for medical applications. They can be used to create scaffolds to which living cells can attach themselves facilitating the systematic creation of biological tissues. The 3d printer could also be used to create tailor made construction parts for biomedical technology or nanotechnology.
  • Seagate has become the first hard drive maker to achieve the milestone storage density of 1 terabit (1 trillion bits) per square inch, producing a demonstration of the technology that promises to double the storage capacity of today’s hard drives upon its introduction later this decade and give rise to 3.5-inch hard drives with an extraordinary capacity of up to 60 terabytes over the 10 years that follow.
  • Device news032412

    1. 1. Device News 03. 24. 12
    2. 2. Photonic Crystals• High temperature photonic crystals instead of batteries?
    3. 3. Terahertz Polarizer• Allows 100% to pass or blocks 99% – Applications for security and for communications
    4. 4. Metamaterials• Negative refraction and other fun and profitable possibilities• Infrared metamaterial phase holograms• Boosting wireless power transfer
    5. 5. Hacking Matter
    6. 6. Hacking Matter – Designer Electrons
    7. 7. More Designer Electrons
    8. 8. Chips• HP Corona – 256 microprocessor chip hooked together optically• 3D graphene electronics• Straintronics
    9. 9. Straintronics
    10. 10. 3D Printer with nano precision
    11. 11. Seagate terabit per square inch drives